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Re: [JC] update conflict handling
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Re: [JC] update conflict handling

  • Subject: Re: [JC] update conflict handling
  • From: Stamenkovic Florijan <email@hidden>
  • Date: Sat, 11 Jul 2009 10:13:16 -0400
Hi Chuck,

On Jul 10, 2009, at 23:32, Chuck Hill wrote:

Hi Flor,


On Jul 10, 2009, at 10:32 AM, Stamenkovic Florijan wrote:

Hi all,

I am implementing update conflict handling based on the info here:

http://developer.apple.com/documentation/webobjects/Enterprise_Objects/UpdateStrategies/UpdateStrategies.html

That is a little misleading. It only applies to OL conflicts across instances (or EOF stacks).

Huh, I totally missed that... Well, not my primary concern right now, as the code never gets reached.

However, it seems that in a JavaClient scenario the update fails before saveChanges() is ever called on an editing context being saved. This means that I can't use an overridden saveChanges() in an EC subclass to catch the adaptor exception caused by the conflict, nor can I use the context delegate to deal with the exception. So, I am not sure where to intercept the exception... Or how to deal with this... Perhaps someone has some experience / an idea about this?

Well, not really. This is one of the very rare instances when I get to observe that JC is actually more sophisticated in this area than regular WO is. Regular WO just silently merges the changes from other editing contexts (problematic when the other EC is form another session). It looks like JC actually catches this and, at least sort of, handles it.

Somehow, you are going to have to handle this earlier than expected. 

That was my impression too.

I am not sure how.

Bummer. I was kind of hoping you'd come up with something involving parts of the EOF that I am not that familiar with. Hm, do you know perhaps of a way to simply turn optimistic locking off in EOF, so that last write always wins?

You could try the documentation. :-P

Did that already... Since it is the EODistributionContext that throws the exception, that is where I started. However, even though it deals with this, it's public API and docs don't even mention update conflicts. Nor does the delegate. So, seeing that you didn't come up with some lower level EOF magic, I would not know where to look. But, I will browse some more in the JC distribution classes. Maybe something there deals with this... I don't think it does though, I've read most of the docs for that stuff and don't recall update conflicts ever being mentioned.

However, seeing that WOJC explicitly deals with update conflicts, it would be reasonable to assume that it is possible to gracefully resolve them. That assumption by itself isn't worth much though :)

Will dig a bit more.

Thanks,
F

Chuck



Below is the server side stack trace of the update exception...

TIA,
F


[2009-7-10 17:20:38 GMT-00:04] <WorkerThread10> Server exception: Optimistic locking failure: The object with global ID _EOIntegralKeyGlobalID[Company (java.lang.Integer)23] has been changed by another client
[2009-7-10 17:20:38 GMT-00:04] <WorkerThread10> java.lang.IllegalStateException: Optimistic locking failure: The object with global ID _EOIntegralKeyGlobalID[Company (java.lang.Integer)23] has been changed by another client
at com .webobjects .eodistribution .EODistributionContext ._throwOptimisticLockingFailureForGlobalIDIfNecessary (EODistributionContext.java:829)
at com .webobjects .eodistribution .common ._EOSavingProxy.replacementEOInEditingContext(_EOSavingProxy.java: 156)
at com .webobjects .eodistribution .EODistributionContext ._replacementObjectForDecodedObject(EODistributionContext.java:882)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun .reflect .DelegatingMethodAccessorImpl .invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com .webobjects.foundation.NSSelector._safeInvokeMethod(NSSelector.java: 122)
at com.webobjects.foundation._NSDelegate._perform(_NSDelegate.java: 223)
at com.webobjects.foundation._NSDelegate.perform(_NSDelegate.java: 159)
at com .webobjects .eodistribution .common ._EOReferenceRecordingCoder .decodeObject(_EOReferenceRecordingCoder.java:619)
at com .webobjects .eodistribution .common ._EOReferenceRecordingCoder .decodeObjects(_EOReferenceRecordingCoder.java:649)
at com.webobjects.foundation.NSArray.decodeObject(NSArray.java:1326)
at sun.reflect.GeneratedMethodAccessor18.invoke(Unknown Source)
at sun .reflect .DelegatingMethodAccessorImpl .invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.webobjects.eodistribution.common._EOReferenceRecordingCoder $_Decoder.decodeObject(_EOReferenceRecordingCoder.java:767)
at com .webobjects .eodistribution .common ._EOReferenceRecordingCoder .decodeObject(_EOReferenceRecordingCoder.java:611)
at com .webobjects .eodistribution .common ._EOReferenceRecordingCoder .decodeObjects(_EOReferenceRecordingCoder.java:649)
at com .webobjects .eodistribution .common._EOServerInvocation.decodeObject(_EOServerInvocation.java:66)
at sun.reflect.GeneratedMethodAccessor17.invoke(Unknown Source)
at sun .reflect .DelegatingMethodAccessorImpl .invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.webobjects.eodistribution.common._EOReferenceRecordingCoder $_Decoder.decodeObject(_EOReferenceRecordingCoder.java:767)
at com .webobjects .eodistribution .common ._EOReferenceRecordingCoder .decodeObject(_EOReferenceRecordingCoder.java:611)
at com .webobjects .eodistribution .common ._EOReferenceRecordingCoder .decodeObjects(_EOReferenceRecordingCoder.java:649)
at com.webobjects.foundation.NSArray.decodeObject(NSArray.java:1326)
at sun.reflect.GeneratedMethodAccessor18.invoke(Unknown Source)
at sun .reflect .DelegatingMethodAccessorImpl .invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.webobjects.eodistribution.common._EOReferenceRecordingCoder $_Decoder.decodeObject(_EOReferenceRecordingCoder.java:767)
at com .webobjects .eodistribution .common ._EOReferenceRecordingCoder .decodeObject(_EOReferenceRecordingCoder.java:611)
at com .webobjects .eodistribution .EODistributionContext .responseToClientMessage(EODistributionContext.java:560)
at com .webobjects .eodistribution .WOJavaClientComponent .handleClientRequest(WOJavaClientComponent.java:1148)
at com .webobjects .eodistribution .WOJavaClientComponent.invokeAction(WOJavaClientComponent.java:445)
at com .webobjects .appserver ._private .WOComponentReference.invokeAction(WOComponentReference.java:127)
at com .webobjects .appserver ._private.WODynamicGroup.invokeChildrenAction(WODynamicGroup.java: 105)
at com .webobjects .appserver._private.WODynamicGroup.invokeAction(WODynamicGroup.java: 115)
at com.webobjects.appserver.WOComponent.invokeAction(WOComponent.java: 1079)
at com.webobjects.appserver.WOSession.invokeAction(WOSession.java: 1357)
at com .webobjects.appserver.WOApplication.invokeAction(WOApplication.java: 1745)
at com .webobjects .appserver ._private .WOComponentRequestHandler ._dispatchWithPreparedPage(WOComponentRequestHandler.java:206)
at com .webobjects .appserver ._private .WOComponentRequestHandler ._dispatchWithPreparedSession(WOComponentRequestHandler.java:298)
at com .webobjects .appserver ._private .WOComponentRequestHandler ._dispatchWithPreparedApplication(WOComponentRequestHandler.java:332)
at com .webobjects .appserver ._private .WOComponentRequestHandler ._handleRequest(WOComponentRequestHandler.java:369)
at com .webobjects .appserver ._private .WOComponentRequestHandler .handleRequest(WOComponentRequestHandler.java:442)
at com .webobjects .appserver.WOApplication.dispatchRequest(WOApplication.java:1687)
at com .webobjects .appserver._private.WOWorkerThread.runOnce(WOWorkerThread.java:144)
at com .webobjects .appserver._private.WOWorkerThread.run(WOWorkerThread.java:226)
at java.lang.Thread.run(Thread.java:613)
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--
Chuck Hill             Senior Consultant / VP Development

Learn WO at WOWODC'09 East in Montréal this August!
http://www.wocommunity.org/wowodc09/east

http://arstechnica.com/apple/news/2009/07/webobjects-sliced-from-106but-prognosis-of-death-premature.ars


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 >[JC] update conflict handling (From: Stamenkovic Florijan <email@hidden>)


 >Re: [JC] update conflict handling (From: Chuck Hill <email@hidden>)






    

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